Nickel complexes corroles

Similarly, the corresponding nickel complex, based on ESR spectroscopy, should be formulated as a nickel(II) corrole-71-radical. The iron corroles exist in the oxidation state + 111 or + IV depending on the nature of additional axial ligands. 

N-containing, in cobalt(III) complexes, 7, 28 in nickel complexes, 8, 120 palladium complexes, 8, 276 synthetic applications corroles, 1, 70... 

The cobalt(II) corrole anion prepared as above was characterized primarily by electron spin resonance (esr) and absorption spectroscopy. When prepared via sodium film reduction, the cobalt(II) corrole oxidizes rapidly to the corresponding Co(III) corrole on exposure to air. When prepared by the other methods, it is moderately stable in air in the presence of a reducing agent. Attempts to prepare the neutral form of the initial Co(II) corrole anion, by protonation with perchloric acid, resulted in formal oxidation to the Co(III) derivative. Interestingly, further protonation of the Co(III) corrole with perchloric acid led to what appeared to be a protonated Co(III) corrole. Certainly, the absorption spectrum of this species is similar to that of the corresponding neutral nickel(II) corrole complex. However, the exact nature of this protonated material has not been fully elucidated. 

It is interesting to note that although A-alkyl Ni(II) corroles can be prepared via the alkylation of N-unsubstituted nickel(II) corroles, the corresponding metal-free A-alkyl corroles appear reluctant to form stable Ni(II) complexes when treated with nickel(II) ions. It is possible, however, to prepare strong palladium(II)... 

Ghosh A, Wondimagegn T, Parusel ABJ (2000) Electronic structure of gallium, copper, and nickel complexes of corrole high-valent transition metal centers versus non-innocent ligands. J Am Chem Soc 122 5100-5104... 

Zn2+ correlate can be obtained, as pyridinium salt, by reaction of corrole with zinc acetate in pyridine [25] in a procedure similar to that reported for the preparation of nickel and palladium complexes of corrole [11]. The zinc derivative is not paramagnetic and its formulation has been made on the basis of its proton NMR spectrum. Attempts to isolate the neutral zinc complex have been unsuccessful. 

The first example reported in the literature is the cyclization of dihydrobilin to octadehydrocorrin [51-54]. The reaction is catalyzed by the presence of nickel or cobalt salts. As in the case of corrole and its metal complexes such ring closure reaction has been carried out in alcoholic solution, it is oxidative and base catalyzed. It has been demonstrated that the formation of the corrin ring is part of an equilibrium where the oxidative ring closure is coupled with a reductive ring opening reaction [55]. 

It was found that addition of hydroxide anion in dimethylformamide or dimethylsulfoxide to metal(II) corrole complexes results in the appearance of much sharper absorption bands relative to the starting compounds. These findings were considered consistent with the idea that an anionic, 18 Jt-electron aromatic corrole complex (e.g., 2.119) is formed as the result of what appears to be a formal deprotonation process (Scheme 2.1.25). That deprotonation actually occurs was inferred from acid-base titrations involving nickel(II) and copper(II) corroles. The conclusion that these species are anionic aromatic compounds came from an appreciation that their electronic spectra resemble those recorded for divalent metallo-porphyrins. In any event, the anion that results was found to be quenched upon acidification, regenerating the corresponding non-aromatic metallocorroles. ... 

Will S, Lex J, Vogel E, Schmickler H, Gisselbrecht JP, Haubtmann C, Bernard M, Gross M (1997) Nickel and copper corroles well-known complexes in a new light. Angew Chem Int Ed Engl 36 357-361... 

One of the strongest nucleophiles known is the complex-bound Co(I) ion (22, 23). In this form vitamin Bj2 mediates a myriad of remarkable transformations. Methylation of Ni(II) corrole anions occurs at the nickel (24). 

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